Patent GB-510525-A (GB)
Title: Methods and arrangements for the determination and indication of the efficiency and flue gas loss of a boiler
IPC: F23N5/00
Filed: 1938-01-31
Abstract: 510,525. Indicating efficiency of steam boilers. GERMER, W. E. Jan. 31, 1938, Nos. 3016 and 17668. [Class 106 (iv)] A method of indicating the efficiency or flue gas loss of a steam boiler in percentages comprises means for measuring the quantity of heat E. in the flue gas flowing from the boiler, means for measuring the quantity of absorbed heat E 2  in the steam flowing from the boiler, means for the continuous division of one of said quantities by the other and giving this last means a pointer turning over a scale which contains the function of this quotient to the boiler efficiency "#" or flue gas less Va as represented by the. formulae "a" being a constant. As shown in Fig 1, fuel is supplied at 12 to the boiler 10 the water tubes 14 of which are connected to a steam drum 16 from which a pipe 18 leads to any steam consuming apparatus. Baffles 20 divide the boiler into several passes terminating in. a flue 22 connected to a stack. An orifice 24 in'the pipe 18 is connected to a steam flow meter 26 in turn connected to a rheostat 28 moved proportionately to steam flow. The gas flow is measured by a Venturi meter 30 in the flue 22 having connection to a Sow meter 32 connected to a rheostat 34. The gas temperature is measured by a thermometer 36 extending into the Venturi pipe. A temperature responsive instrument 38 is connected to the thermometer 36 and to a rheostat 40. The steam flow, gas flow, and gas temperature are preferably separately indicated on the instruments 42, 44, 46. For the boiler efficiency "#" each of the instruments 26, 32 and 38 is equipped with a second electric rheostat 48, 50, 52. The resistances are so compounded in a bridge circuit that the instrument 54 reads boiler efficiency. In a mechanical form of efficiency indicator the steam flow meter operates a logarithmic cam which moves the scale while a pointer is moved over the scale by a logarithmic cam operated by the gas flow meter. The direct indication of boiler efficiency may be given by an electric quotient meter having an alternating current ring iron measuring system in which three windings are arranged on the same frame. Two of them are connected to the rheostat of the gas flow and flue gas meters respectively. The third is connected to the steam flow meter. All three rheostats are operated by logarithmic cams from the meters the steam meter cam being operated in the opposite direction to the other two so that the instrument reads a quotient representing the efficiency. Fig. 5 shows an efficiency meter comprising a double indicating instrument with two electric measuring systems for remote transmission. One system has a pointer 100 moving over a scale D of steam flow. The other carries on its pointer 102 the triangular scale 104 with convergent scale 106 for boiler efficiency. The. pointer 102 shows on scale G the value of the. factor (Rm-t), where Rm, is the :gas flow in cubic metres per second at O‹C, and Rt and t the temperatures of the flue gas and air respectively. The second Rm (Rt - t) scale has been calculated in this example for a boiler with an average boiler efficiency @@ of 70 per cent This coincides on scale 106 with the position of pointer 102 or with the vertical height of the triangle. The vertical line indicates 70- per cent, on the triangular efficiency scale 106. The indicating line 108 starts in the point G, the zero of the Rm (Rt - t) scale, and moves to a point H in the base line of the triangle and a distance M away from the'maximum of the scale corresponding to the distance of the left starting point of the triangle to the vertical line of 70 per cent.- The triangular scale shows a part of the horizontal divisions from 2 to 5 per cent. of the D-scale reduced to height of the triangle. The left side of the triangle scale intersects the indicating line 108 at a value of D of nearly 3 checking the position of the centre line of pointer 102 on the D-scale below. The intersections of the D-pointer 100 with the horizontal line 3 shows an efficiency of 72.4 per cent. for actual boiler efficiency., A form of simple slide rule is described having logarithmic scales for flue gas flow, flue gas temperature and steam flow together with an efficiency scale.